Car adds backpack to give more go

It sounds so simple that it's a wonder car makers didn't think of it earlier.

German specialist vehicle maker Rinspeed has found a way of attaching a "backpack" to the electric Smart ForTwo car which is being considered for sale in Australia.

This bolt-on bustle contains extra batteries to give the Smart a longer range for times when you want to go further.

It also offers extra room - either covered with a wagon shape or as a ute tray - for personal luggage or for commercial cargo.

Like pizzas. "It creates mobility 'a la carte'," says Rinspeed.

"The 'backpacks' carry out their assigned tasks depending on current need. They cleverly solve the much-debated operating range problem that electric vehicles suffer from - neither unnecessary space nor superfluous weight is being transported."

Dock+Go is the work of Swiss car designer Frank Rinderknecht and his Rinspeed team. It goes on display at next month's Geneva motor show but has a good chance of production.